1. Field of the Invention
The present invention relates to a compound-eye imaging device.
2. Description of the Related Art
A compound-eye imaging device is known as an imaging device to realize a thin camera as disclosed, for example, in Japanese Laid-open Patent Publication Hei 10-84104. The compound-eye imaging device (image sensor) according to Japanese Laid-open Patent Publication Hei 10-84104 has a lenslet array of multiple integrated optical lenses (lenslets), and a solid-state imaging element (photosensor array) for capturing multiple unit images formed by the optical lenses.
Generally, in order to reduce the size of the compound-eye imaging device, the optical lenses are densely formed, and the unit images formed by the optical lenses are also formed close to each other on the solid-state imaging element. However, a compound-eye imaging device having densely formed optical lenses to form unit images close to each other has a disadvantage that light entering through each optical lens to form each unit image corresponding to the each optical lens may interfere with light (hereafter referred to as “stray light”) entering through an adjacent optical lens or lenses, thereby degrading each unit image. This may cause a combined image or a panoramic image produced from the unit images to be no good.
In order to overcome this disadvantage, it is known to provide, between the solid-state imaging element and the optical lenses, walls (spacers in the compound-eye imaging device of Japanese Laid-open Patent Publication Hei 10-84104) by which light propagation paths of lights emitted from the optical lenses are partitioned from each other. However, such compound-eye imaging device has other problems. For example, the space between the solid-state imaging element and the optical lenses is narrow. Thus, there is a problem that a complicated and time-consuming work is unavoidably required to accurately incorporate the walls into the narrow space, causing the manufacturing process of the compound-eye imaging device to be complicated.
In addition, although components of light, which are emitted from each optical lens, and which have large emission angles and thus are likely to become stray light, are prevented by the provision of the walls from propagating any further to reach an adjacent unit image or images, the components of light reflected from the walls may reach the solid-state imaging element which is located in an area partitioned by the walls and which forms a unit image corresponding to the each optical lens, thereby interfering with and degrading such unit image itself Thus, in order to prevent the generation of stray light and the degradation of each unit image, the wall surface of the walls is required to have an extremely low reflectance e.g. by selecting the material of the walls. However, this further complicates the manufacturing process and increases the cost of the compound-eye imaging device.